> To prove something consistent, you have to define what it means for it> to be consistent. To prove a system of formal wffs consistent, we> have a (recursive) function f over wffs that maps a wff into its> negation, and it is not consistent iff there is a w such that w and> f(w) are provable. But how does this apply to ZFC? ZFC is a> collection of statements that are best expressed in English - attempts> to formalize them create debate as to what a particular expression> means. In other words, where is the formal syntax that precisely> specifies the axioms and rules of ZFC? There are none - it is not> that formal.